Figure 5

Figure 5

Adaptive evolution of fright reaction genes in zebrafish. Comparison of the proportions of genes showing evidence of positive selection between differentially expressed and unbiased genes. The percentage of positively selected genes was identified using site mode (A) and branch site model (B) using codeml. (C, D) Codon usage bias in differentially expressed versus unbiased genes, as measured by frequency of optimal codons (Fop) (C) and effective number of codons (D). (E) Breadth of expression between differentially expressed and unbiased genes measured by the specificity index value (τ). Significant differences were indicated by the asterisks, based on Chi-squared test, *P < 0.05, **P < 0.001. NS means non significant.